1. Field of the Invention
The present invention relates to apparatuses for smelting sulfide copper concentrates to produce blister copper.
2. Discussion of the Background
Copper smelting facilities can be broadly divided into a continuous smelting process, for example a Mitsubishi process, and a batch process involving batch type smelting furnaces and converters.
The conventional batch processing will be explained with reference to FIG. 3 showing a facility configuration, and to FIG. 4 showing a process flow chart.
As shown in FIG. 3, the batch processing facility comprises: a flash smelting furnace 40 for producing a matte (containing a mixture of primarily copper sulfides and iron sulfides) and a slag (containing gangue minerals, fluxes and iron oxides) by melting finely divided and dried copper concentrates together with oxygen-enriched air or high temperature air stream to melt and oxidize; matte transport means 41 having a ladle 50 and a crane 51 for transporting the molten matte produced in the smelting furnace 40 to a converter 42 (to be described later); a batch operated converter 42, for example a Peirce Smith converter for making blister copper by further oxidizing the molten matte brought thereto by the matte transport means 41; a ladle 57 and a crane 59 for transporting the blister copper produced in the converter 42 to a refining furnace 44 (to be described later); and a plurality of refining furnaces 44 for making refined copper (anode copper) of higher copper grade. In FIG. 3, only one of the refining furnaces is shown.
The smelting furnace 40 has a furnace body 40a, and on the top section of the furnace body 40a, there are provided a charging nozzle 45a for admitting the copper concentrates, and inlet opening 45b for admitting oxygen-enriched air, fluxes, fuels and other raw materials into the smelting furnace 40. Reference numerals 46 and 47 respectively refer to a slag tapping hole and a matte tapping hole, and the matte tapping hole 47 is provided with a matte discharge pipe 48 having a valve 48a.
The matte transport means 41 has two support columns 49 (only one column being shown in FIG. 3) and a crane support section (drive section) 41a, the crane support section 41a being provided with a crane 51 which can suspend a ladle 50. The crane 51 is transported by the crane support section 41a and along the crane support section 41a between the flash smelting furnace 40 and the converters 42. The crane support section 41a is also provided with an additional crane 59 which can suspend a ladle 57.
The converter 42 is a batch type furnace, and the furnace body is provided with an inlet opening 53, which can be opened or closed with a lid member 53a. The reference numeral 54 refers to a slanting/rotation device.
The crane 59 moves between the converter 42 and the refining furnace 44 along the crane support section 41a.
The refining furnace 44 is provided with an inlet opening (not shown) at the top, and a discharge opening 63, and the inlet opening is opened or closed with a lid member 60. The reference numerals 61, 62 and 64 respectively refer to gas discharge opening, fuel burner and slanting/rotation device.
The process of smelting using this batch type facility will now be explained.
As shown in FIGS. 3 and 4, copper sulfide ores are processed first in a preparation facility 66 to carry out, for example, drying, sintering and pelletizing. The prepared copper concentrates are charged into the smelting furnace 40 through the charging nozzle 44 together with fuel and fluxes through the inlet opening 45 into the smelting furnace 40. The concentrates are melted in the smelting furnace 40, and the melt is separated by the density difference to an upper slag layer and a bottom matte layer. In the process, iron in the concentrates is oxidized, and combines with SiO.sub.2 added as a flux to be included in the slag, and copper is concentrated in the matte as a molten sulfide. The matte containing copper as the primary ingredient is withdrawn from the matte discharge pipe 48 of the smelting furnace 40 into the ladle 50. The matte tapping step from the smelting furnace 40 in the smelting process is carried out in general as a batch process.
The ladle 50 is moved by the crane 51 to above the converter 42, and the molten matte in the ladle 50 is charged into the converter 42 through the inlet opening 53. The converter 42 is also charged with fluxes through the inlet opening and oxygen-enriched air is blown in through tuyers (not shown), and the copper sulfides in the matte are oxidized to produce blister copper. The blister copper produced in the converter 42 is withdrawn through the inlet opening 53, transferred to the ladle 57, transported by the crane 59, and charged into the refining furnace 44 through the inlet opening 60 disposed on the top section of the refining furnace 44. In the refining furnace 44, the blister copper is further refined to a higher grade copper, thus resulting in a refined copper.
The refined copper melt is withdrawn from the discharge hole 63, cast into copper anodes to be forwarded to an electrolytic refining tank 67 to produce electrolytic copper. Subsequently, the copper is melted in a reverberatory furnace, for example, and cast into billet cakes (refer to FIG. 4).
In the processes carried out in the smelting furnace 40 and the converter 42, the flue gases 70 generated contain a high percentage of sulphur dioxide gas, which is treated with water in a sulfuric plant 69 to produce sulfuric acid 71. Because the converter 42 operates on a batch system, the flue gas volume and the concentration of sulphur dioxide gas in the flue gas generated vary with time in a manner of square waves, i.e. high during the operational period and extremely low during tapping and discharging periods. It is therefore, necessary that the processing capacity of the sulfuric acid plant 69 be established to enable processing of the maximum volume of flue gas and the concentration of the sulphur dioxide gas in the flue gas.
In the conventional batch processing facility described above, because the acid plant processing capacity is geared to cope with the period of maximum production of flue gas and the concentration of sulphur dioxide in the flue gas, there is a problem that the capital cost for the acid plant becomes high.
Further, when a number of converters are provided to increase the production capability of blister copper, the number 8 peripheral facilities such as cranes must be increased and the attendant area for the added facility must also be provided. The overall result is a significant increase in the capital cost for the copper smelting.
The present inventors discovered that the above-noted problem can be resolved by replacing the bath processing converter with a continuous converting furnace for processing of copper matte to blister copper, because the continuous converting furnace produces relatively less flue gas compared with the batch type converter, and the volume of the flue gas generated and the concentration of sulphur dioxide in the flue gas is evenly spread over the operational period.
However, to enable to utilize a continuous converting furnace, the molten matte must be continuously charged into the continuous converting furnace. To do this, an elevational difference must be provided between the ground-level smelting furnace and the continuous converting furnace. For example, if the differential elevation is provided as shown in FIG. 5, by directly connecting the ground-level smelting furnace 40 with the continuous converting furnace 42a and the refining furnace 44 by means of launders 72, 73, the ground GL must be excavated to accommodate the continuous converting furnace 42a and the refining furnace 44. This approach ultimately requires vast facility modification expenses.
Another problem associated with the above launder connection approach is that, because the molten matte is withdrawn in batches, the flow of molten matte will be discontinuous, resulting in drying up of the launder and a high maintenance cost.